Jack



R. S. BAKER A ril 6, 1965 JACK 4 Sheets-Sheet 1 Filed Sept. 30, 1965 R.S. BAKER A ril 6, 1965 JACK 4 Sheets-Sheet 2 Filed Sept. 30, 1963INVENTOR P05 52 7 62 .Bfl/(EB Er W ATTORNEYS April 6, 1965 R. s. BAKERJACK Filed Sept. 30, 1963 4 Sheets-Sheet 2 INVENTOR fad-file r 62 BAKE-BR. S. BAKER A ril 6,. 1965 JACK 4 Sheets-$heet 2 Filed Sept I50, 1963INVENTOR F05 5e 7- 63 34x52.

ATTORNEYS April 6, 1965 R. s. BAKER 3,176,962

JACK

Filed Sept. 30, 1963 4 Sheets-Sheet 3 ATTORNEYS a INVENTOR Q Poms-1e7-6. 314K516 5 I United States Patent 3,176,?62 JACK Robert S. Baker, R0.Box 11476, Tampa, Fla. Filed Sept. 30, 1963, Ser. No. $12,749 it)Claims. ((11. 254-67) This invention relates to jacking devices, andmore particularly to such devices of electro-mechanical nature.

While the jacking device of the present invention is suitable for use inany jacking operation, and can be utilized as a substitute mechanismwherever fluid operated cylinder jacks are called for, it is speciallyadapted for use as a portable jack for tightening, or tensioning,strands, cables, and like members. It is in this embodiment that thepresent disclosure will be made.

At the present time in this country, all jacking in connection withtensioning cables, such as required for making prestressed concretemembers for example, is done by means of hydraulics. Much of this workhas been done by simultaneous tensioning of a plurality of cables. Wherethe member to be formed was a large one, very heavy equipment wasrequired, including motor, pumps, hydraulic lines, by-passes, high andlow pressure systems, etc. Even when smaller members are made andlighter equipment is used, the many components listed above arerequired. Single-strand jacking is becoming increasingly popular, but inthis case, also, the hydraulic equipment is cumbersome, expensive andrelatively ineiiicient.

The general object of the present invention is to provide anelectro-mechanical jack which is simple, economical, light weight and ofhighly increased efiiciency.

A more specific object is the provision of a jack of this kind which isadapted to engage, and exert a pulling force upon, strands, cables andlike members to pull, remove the slack from, and/ or tension them.

Another object is to provide a jack suitable for cable tensioning whichis portable and can be moved from strand to strand.

A further object is the provision of a jack which operates upon amotor-driven ball screw principle.

Still another object of the invention is to provide a jack which willgive visual indication of the pulling force imposed upon a strand, orcable, so that predetermined tension may be applied to the strandirrespective of the length of the pull or the amount of slack in thestrand at the outset.

Other objects of the invention will become apparent from the followingdescription of one practical embodiment thereof, when taken with thedrawings which 'accompany, and form part of, this specification.

In the drawings:

FIGURE 1 is a side view of a portable electro-mechanical jack embodyingthe principles of the present invention;

FIGURE 2 is a top plan view of the jack, parts being broken away to showthe interior;

FIGURES 3 and 3 together constitute a vertical section through the jack;

FIGURE 4 is a vertical transverse section through the pulling head andguide tube, taken on the line l4 of FIGURE 3 FIGURE 5 is a verticaltransverse section through the jack at the load indicator position, andis taken on the line 55 of FIGURE 1 FIGURE 6 is a fragmentary sectiontaken on the line s-s of FIGURE 1, illustrating the position of a limitswitch;

FIGURE 7 is a fragmentary section through the gear casing, taken on theline 7-7 of FKGURE 3 and FIGURE 8 is a fragmentary section taken on theline 8-8 of FIGURE 4, showing the means employed to ob- 3,.l'i6,%2Patented Apr. 6, 1965 tain a visual indication of the pulling forceapplied to a strand engaged by the jack.

In general, the jack is a unitary tool, in which a motor is used tocause a ball screw to move axially and draw a pulling head linearly ofthe device relative to a head guide which acts as an abutment member.The guide is made in two sections with compressible members between thesections, to provide for relative movement between the sections underload and actuation of a load indicator. Means are also provided to showthe extent of relative movement between the head and head guide.

Referring to the drawings in detail, the jack is shown as including anelongated body 1, a gear casing 2, an electric motor 3, and acombination stand and handling frame 4.

The body 1 is composed for the greater part of its length of a guide 5,having a forward section 6 and a rear section '7. The two sections haveannular flanges 8 and 9 at their adjacent ends, and are coupled inlong'tudinal alignment by bolts 10. Belleville spring units 11 aremounted on the shanks of bolts 10, and seat in recesses 12 and 13 in therespective flanges 8 and 9. The bolts are drawn up evenly to place theBelleville units under a desired predetermined compression. The purposeof the springs and their action will be described later.

Guide 5 is substantially U-shaped in cross-section, being open along thefull extent of its top. The open top provides a slot 14 along which anindicator (to be described) may move. It also allows free access to thepulling head for engaging and disengaging cable. The outer end of theguide, that is the end farthest trom the gear casing 2, is bridged by anabutment plate 15, welded around its edges to the sides and bottom ofthe guide 5. The plate is notched from its top edge to below the centerof the guide to provide an entrance notch 16 for cable to be tensioned.The guide is strengthened along its upper edges at the side of slot 14by means of rods 17 extending throughout the length of each of thesections of the guide. The rods are welded to the guide walls alongtheir full lengths.

The back end of section 7 of the guide fits within a recessed seat 18 ina cap assembly 19 and is welded in place. The opposite side of the caphas an annular projection 20 about which a cylindrical housing member 21fits. The cap and housing member have matching flanges 22 and 23 and arebolted together. Cap 19 ha another recessed seat 24 in its face oppositeseat 18 to receive a bearing 25. The cylindrical housing member is alsorecessed in its end, as at 26, to seat a bearing 27. Bearing 25 servesas an end thrust bearing under load, while hearing 27 receives the hubof a gear 28. The gear hub fits over the end of a ball-bearing nut 29which has its other end mounted in a ring 3! seated in a bearing 31carried by the housing member 21.

Gear 28 is fixed to the nut 29 and is driven by a spur gear 32 mountedon shaft 33 of motor 3. The motor is bolted to a motor platform 34carried by the cap 19. The gears 28 and 32 are enclosed within casing 2for protection of the gears and operators of the jack.

The gear casing has a rearwardly projecting sleeve 35 which supports aring 36. This ring has a collar 37 to which is attached one end of acollapsible boot 38.

Mounted within the nut 29 is a ball-bearing screw 39. The screw extendsthrough the nut and along guide 5 in a forward direction. It projects tothe rear into boot 38, and has a projection 40 at its rear end to whichthe outer end of the boot is connected. As the screw moves to the rear,boot 38 will extend, and when the screw moves in an opposite directionthe boot contracts, or collapses.

Screw 39 and nut 23 are a ball-bearing unit of well known type. The nuthas thread-like grooves 41 on its inner face, and a plurality of balls42 run in the threads and 27.

At the forward end of the screw 39 there is a pulling head 45, which isthreaded onto a forwardly projecting threaded stud 46 of the screw 39.The head is U-shaped in cross-section, being open at the top, andcarriesa plate 47 at its forward end. The plate is notched from itsupper edge to provide a cable slot 48. Spaced'from the end plate 47, abaffle 49 inclines from the head bottom rearwardly. The area from theend plate 47 to the baffie forms a seat for cable anchors fitted aboutthe ends of cables to be tensioned.

At the back end of the pulling head, there is a pointer 50 which isscrewed to the head. The pointer moves over a scale 51 marked along thetop edge of guide 5, adjacent one edge of slot 14.. As the head movesalong the guide, the distance travelled will be indicated by theposition of the pointer on the scale.

In order to protect the screw 39, and other internal 'parts of thedevice, from dirt, and yet permit free movement of the pointer over theguide upper edge, a flexible cover 52 extends over the slot. Theflexible cover also permits exit and entry of cable and anchor at anyconvenient position. The cover is attached to the opposite side of theguide from that carrying scale 51 by means of angle brackets 53.

The jack stand, or handling frame, 4 is composed essentially of aU-shaped main frame 54 having its bridge underlying the guide tube ofthe jack body, and the ends of its legs secured to the forward face ofthe gear casing 2. A leg 55 projects downwardly from the center of thebridge directly below the guide 5. 'Leg 55 together with a flattenedbase 56 on the gear casing 2 provide surface I contacting members tosupport the jack. The jack can be lifted and transported, or otherwisehandled by means of this stand. If desired, a lifting device can beconnected toeyes 57 attached to the frame.

It is desired that the pulling force exerted on a a cable be known atall times, and, to this end, the jack carries a pressure indicator 58,mounted on a bracket 59', secured to the rear section 7 of the guide 5.An operating rod 60 extends forwardly from the indicator throughopenings 61 and 62 in the guide flanges 9 and 8, respectively. A setscrew 63 fixedly connects the operating rod in the flange 8 of theforward section 6 of guide 5. With this arrangement, any force whichcauses. compression of the Belleville units between flanges 8 and 9 willcause the op' erating rod 60 to move relative to the indicator 53, withthe result that the indicator will show the force requiredto cause themovement. The indicator will have its face ex- A posed through anopening 64in a'housing member 65 connected to an extension 66 at the topof the guide section 7 adjacent the flange 9. The bottom edge of thehousing will be hooked under the adjacent leg of'the U-frame 54 of thestand.

The motor 3 will be a reversible one and will be controlled by a switch67 located on the motor. If desired, limits switches 68 and 69 may beused to prevent travel of the screw 39 beyond predetermined limits.Switch ss can be mounted on a gusset plate 75) beneath the motorplatform 34, and have its trip arm 71 contacted, and actuated, by thepointer 50 when the pulling head has reached its limit of movement in apulling direction. Switch 65 is shown mounted in the sleeve projectingfrom the gear casing. Its trip arm 72 may be contacted by the screwextension 40, or any other convenient part of the screw assembly to stopreverse movement of the screw whenthe 4 pulling head is in properposition for engaging a cable for tensioning.

In operating the device, the jack will be positioned with its outer endin abutment with a bolster plate of a form in which a prestressedconcrete member is to be made. The jackwill be set in alignment with acable strung along the form bed and through the bolster plate. Theextended end of the cable will lie in the notch 16 of the abutment plate15, and project through the cable slot 48 at the end of pulling head 45with its end lying within the pulling head. A suitable anchor ispositioned on the cable end.

Motor 3 will be started, and this will rotate gears 32 and 28, andthrough them ball-bearing nut 29, to cause screw 3? to move through thenut and the pulling headto move away from the forward'end of the jackbody. The

anchor on the cable end will contact the plate 47 of the pulling head sothat the pulling head will draw the cable with it, first removing theslack from the cable and then tensioning the cable.

It will be apparent that the pulling force of the head is appliedthrough the screw to the ball-bearing nut, and from the nut through thejack body against the member with which the body end is in abutment.Thus, the two points of pressure are the nut and the body end which areon opposite sides of the body coupling at the flanges 8 and 9 with theresult that all of the force is applied through the Belleville springunits.

There will be relatively little pressure applied during the initialtaking up of slack, and the strength and the initial compression of thesprings through tightening of bolts 10, will be such that there will beno movement of the springs and no pressure indication on the indicator58. During the period of slack take up, the pointer 50 will havetravelled a distance over the scale 51 equal to the travel of thepulling head. This point should be noted, as specifications forprestressed concrete members frequently require that cables be tensionedby a predetermined degree of elongation. Having noted the readingon'scale 51 at the end of slack take up, the cable elongation can beaccurately made.

After removing slack, continued movement of the pulling head firstplaces the cable under tension, then progressively increases thattension. The extent of elongation can be precisely checked by scale 51,and indicator 58 will provide continuous visual indication of the pullbeing applied to the cable. When the required cable elongation andpulling force have been achieved, the motor will be stopped. An anchoron the cable can be brought up close to the bolster plate against whichthe jack abuts to hold the cable fast in the head under desired tension.The motor can then be reversed to run the pulling head back to itsstarting position.' As the head starts back, the cable end will contactthe inclined bafile 49 and ride up it to be released from the head. Whenthe pulling head reaches its position of rest, switch 69 will beactuated to break the motor circuit. The jack is then free for movementto the next cable position.

The jack disclosed herein is readily moved from place to place, and is asingle unitary tool. The use of a ballbearing screw as the powertransmission member permits extremely heavy pulls with low power output.Forming the body in two parts with Belleville spring units intervening,so that the springs become a part of the thrust column, permits a singlecontinuous pulling operation to first take up slack, then tension, yetallows for measurement of only the force applied during tensioning. Thisis accomplished by connecting the indicator and its operating rod tomembers opposite sides of the Belleville units. At the same time, thelinear movement of each pulling operation is indicated automatically.

While in the above one practical embodiment of the invention has beendisclosed, it will be apparent that the particular structure shown anddescribed is only for purposes of illustration, and the invention maytake other forms within the scope of the appended claims.

What is claimed is:

1. A jacking device comprising, a body, a portion of the body forming anelongated guide having a free end forming an abutment, a pulling headslidable in the guide, a screw attached to the pulling head, a nutrotatably mounted in the body and threaded upon the screw, the nut beingfixed against bodily movement relative to the body in the direction inwhich the pulling head is slidable, and means to rotate the nutincluding a motor mounted on the body and interconnecting the motor andnut to move the pulling head along the guide, the frame having siderails by which the jacking device can be handled and a leg to supportthe jacking device on the ground.

2. A jacking device as claimed in claim 1, wherein the pulling headcarries a pointer, and there is a scale along the guide over which thepointer moves when the pulling head is advanced along the guide toindicate the distance travelled by the pulling head.

3. A jacking device comprising, a body including an elongated guide, thebody being of two sections arranged end to end, compressible meanspositioned intermediate the body sections to yieldingly separate thesections, means connecting the sections in alignment, one body sectionhaving a free end forming an abutment, the other body section having anut rotatable therein and held against bodily movement, a pulling headslidable in the guide and having means to engage a member to betensioned, a screw connected to the pulling head and threaded throughthe nut, means to rotate the nut to draw the pulling head from theabutment end of the said one body section, a pressure gauge mounted onone of the body sections and having an operating rod attached to theother of said body sections, whereby rotation of the nut will draw thepulling head having a member to be tensioned connected thereby away fromthe abutment end and impose a pressure upon the abutment end through thecompressible means and thereby actuate the pressure gauge to providevisual indication of the tension applied to the member to be tensioned.

4. A jacking device as claimed in claim 3, wherein there is a pointercarried by the pulling head and a scale on the guide over which thepointer moves as the pulling head is drawn from the abutment end toindicate the distance the pulling head is moved.

5. A jacking device as claimed in claim 3, wherein the means to rotatethe nut includes a motor mounted on the section of the body carrying thenut, and power transmitting means between the motor and the nut.

6. A jacking device as claimed in claim 5, wherein there is a frameconnected to that section of the body carrying the nut, the frameincluding side rails by means of which the device can be handled and aleg to support the device on the ground.

7. A jacking device as claimed in claim 3, wherein there is means toadjust the initial pressure on the compressible means.

8. A jacking device as claimed in claim 3, wherein the compressiblemeans are Belleville springs.

9. A jacking device as claimed in claim 8, wherein the means connectingthe body sections in alignment includes means for adjusting the initialpressure on the Belleville springs.

10. A jacking device comprising, a body of two sections arranged end toend, compressible means positioned intermediate the body sections toyieldingly separate the sections, means connecting the sections inalignment, one body section having a free end forming an abutment, theother body section having a nut rotatable therein and held againstbodily movement, a screw connected to the pulling head and threadedthrough the nut and having means carried thereby to engage a member tobe tensioned, means to rotate the nut to draw the screw from theabutment end of said one body section, a pressure gauge mounted on oneof the body sections and having an operating means attached to the otherof said body sections, whereby rotation of the nut will draw the screwhaving a member to be tensioned connected thereto away from the abutmentend and impose a pressure upon the abutment end through the compressiblemeans and thereby actuate the pressure gauge to provide visualindication of the tension applied to the member to be tensioned.

' WILLIAM FELDMAN, Primary Examiner.

MILTON S. MEHR, Examiner.

1. A JACKING DEVICE COMPRISING, A BODY, A PORTION OF THE BODY FORMING ANELONGATED GUIDE HAVING A FREE END FORMING AN ABUTMENT, A PULLING HEADSLIDABLE IN THE GUIDE, A SCREW ATTACHED TO THE PULLING HEAD, A NUTROTATABLY MOUNTED IN THE BODY AND THREADED UPON THE SCREW, THE NUT BEINGFIXED AGAINST BODILY MOVEMENT RELATIVE TO THE BODY IN THE DIRECTION INWHICH THE PULLING HEAD IS SLIDABLE, AND MEANS TO ROTATE THE NUTINCLUDING A MOTOR MOUNTED ON THE BODY AND INTERCONNECTING THE MOTOR ANDNUT TO MOVE THE PULLING HEAD ALONG THE GUIDE, THE FRAME HAVING SIDERAILS BY WHICH THE JACKING DEVICE CAN BE HANDLED AND A LEG TO SUPPORTTHE JACKING DEVICE ON THE GROUND.